SEASONAL AND LONG-TERM VARIATIONS IN WATER-QUALITY OF THE COLUMBIA-RIVER AT REVELSTOKE, BC

The purpose of this study was to analyze six years of water quality da ta collected every four weeks from the Columbia River al Revelstoke to determine the processes controlling water quality and the presence or absence of trends. Plots versus time were used to assess seasonality, while hysteresis diagrams were used to describe processes affecting t he water quality variables through the relationship of water chemistry to discharge. The major ions exhibited seasonality showing high conce ntrations in the winter and low concentrations in the summer, while ot her variables did not exhibit seasonality. The hysteresis diagrams ind icate that the seasonal pattern of major ions is different from natura l systems. The lack of flow relationships for metals and other sedimen t related variables also differs from natural systems. These differenc es result from impact of reservoirs on the river processes. Box-Jenkin s rime-series techniques were used to model and forecast future values for the variables. Revelstoke Dam has a significant impact on the wat er quality processes. No trends over time were found for the water qua lity variables.